Process for controlling blending

ABSTRACT

A process of controlling the blending of components to produce a product composition at a target value for least one characteristic has been developed. The process involves varying the proportion of the components, determining with each variation the change in the value of a characteristic, adjusting the proportion of those components to afford a new composition where the value of the characteristic is numerically closer to the target value, and repeating the steps until the target value of the characteristic is achieved. The process further includes determining blending factors to be used in existing blending equations.

BACKGROUND OF THE INVENTION

A common practice in petroleum refining is to blend products fromseveral different process units, such as straight run gasoline,alkylate, hydrocrackate, reformate, oxygenates, etc., and purchasedcomponents to obtain gasoline in a grade that meets regulatoryrequirements such as minimum octane number, Reid vapor pressure, benzenecontent, and the like. Octane number, as defined by ASTM D2699 forresearch octane number or ASTM D2700 for motor octane number, is anindication of a gasoline's resistance to pre-ignition during thecompression stroke of a piston, and Reid vapor pressure (RVP), asdefined by ASTM D323, is a measure of the ease of evaporation of agasoline and is often indicative of cold start capability.

The blending of various components to form gasoline is a complexprocess. Depending upon refinery configuration, anywhere from five totwelve or more different base stocks are blended to meet regulatoryrequirements. Furthermore, the optimization can involve numerousvariables including regulated parameters, physical properties andcomposition of the final blend, and availability and cost of blendcomponents.

Often in industry, the ratios of the components to be blended aredetermined by charts or mathematical algorithms known as "blendingequations". Such blending equations are well known in the petroleumrefining art and are developed or adapted by each refiner depending uponavailable crudes, refinery configuration, and cost and availability ofblend stock components. Such equations are most frequently used in theblending of components to form a gasoline which meets regulatoryrequirements. Examples of blending equations and their applications aregiven in Cary, J. H.; Handwerk, G. F. Petroleum Refinery Techniques andEconomics; Marcel Dekker: New York, 1984; Chapter 11.

Blending equations typically relate a quantity of gasoline, in moles/Lfor example, at a target value for some characteristic, such as RVP,octane, or percentage composition of oxygenates, to the quantity of eachof the component streams multiplied by the measured value of that samecharacteristic for each component stream. Blending equations also mayindicate significant nonlinearity of gasoline parameters with respect tothe addition of a blend component. For example, RVP generally variesnonlinearly with the addition of butane or methanol.

Using blending equations is further complicated since the value of acharacteristic in a component is not necessarily indicative of the finalvalue of the characteristic in different blended products. For example,the value of a characteristic in the blend may be less than, equal to,or greater than the sum of the proportionate values of thecharacteristic in the blend components. Stated another way, a componenthaving a high octane, may increase the octane of the final blendedproduct by variable amounts depending on the structure of the additionalcomponents being blended. "Blending octane number" is the term typicallyused to express a refiner's experience as to the impact a petroleum basestock will have on the octane of the final gasoline blend.Unfortunately, the blending octane number may vary, especially when theother components of the blend are changed. Therefore, blending octanenumbers are normally estimated by charts, calculated empirically, ormeasured after the gasoline blending is complete.

Due to the described complexities, blending component ratios are usuallyestimated based upon laboratory data or experience. Neither approach isentirely satisfactory, and costly overcompensation and even reblendingis common in the petroleum industry. The present invention meets thedemand for an improved efficient process of controlling the value of acharacteristic in a blended composition by using spectroscopicmeasurements which can be employed on- or in-line and in real-time. Forexample, even though on-line octane monitors have long been available tomonitor a product's octane number, the technology of these monitors issuch that each measurement requires at least 12 minutes, and duringthose 12 minutes the octane number of the product may have changed.Furthermore, controlling blending with these monitors is inefficient dueto the 12-minute delay before the effect of each parameter changebecomes known. Recently, near infrared (NIR) spectroscopy has been usedto determine octane numbers of hydrocarbons thereby providing virtuallyinstantaneous octane numbers since the analysis time is generally onlyabout one minute. U.S. Pat. No. 4,963,745, U.S. Pat. No. 5,223,714, E.P.(0 285 251), E.P. (0 305 090), and W.O. (WO 91/15762) are typical ofdisclosures which teach that NIR spectroscopy may be used to determineoctane number. Many methods of using NIR spectroscopy can be found inthe art, and which specific method is applied in the practice of thisinvention is not as important as the overall contribution of theadvantages of NIR spectroscopy. The same pattern of significantlyimproved response time of NIR spectroscopy as compared to traditionalon-line analyses holds for other characteristics as well as octane.Through applying the advantages provided by on-line and in-line NIRspectroscopy in a new efficient process of controlling blending, thisinvention furnishes a significant cost-reducing alternative to currentblending practices in the petroleum industry.

U.S. Pat. No. 4,963,745, E.P. (0 305 090), and W.O. (WO 91/15762) eachfocused on a specific method for using NIR spectroscopy to measure thevalue of a characteristic. Each also briefly disclosed that itsparticular method may be used to control a blending operation. However,in contrast to our invention, none of the disclosures provide thespecific details of the control process necessary for one skilled in theart to implement the particular method as a control process. U.S. Pat.No. 5,223,714, disclosed using NIR to predict physical or chemicalproperties of the blended product from the absorbance of eachpreblending component. This patent disclosed that such predictions maybe used to control blending, but the focus of the patent was on how tomake the measurements and how to mathematically manipulate thosemeasurements. Our invention allows any suitable spectroscopic andmathematical techniques to be used and instead focuses on the detailedsteps of controlling the blending. E.P. (0 285 251) disclosed an NIRspectroscopic method to determine octane number but did not discloseusing the method to control a blending operation.

SUMMARY OF THE INVENTION

The purpose of this invention is to provide a control process for ablending operation so that the final blended composition is at a targetvalue of at least one characteristic. More specifically, the inventionis directed to controlling the value of at least one characteristicduring the blending of petroleum refining streams to produce a petroleumproduct at a target value for the characteristic. A specific embodimentof the invention is controlling the value of octane number whileblending petroleum refining streams, which are variable and may in factbe varying, to produce blended gasoline of a particular octane number. Astill further specific embodiment is the use of NIR spectroscopy as theanalytical technique to determine the values of one or morecharacteristics. Still another embodiment discloses a process of moreprecisely determining blending octane numbers to be used in existingblending equations.

The novel features of the present invention will be better understoodfrom the following detailed description, considered in connection withthe accompanying drawing. It should be expressly understood, however,that the drawing is for the purposes of illustration and descriptiononly and is not intended as a definition of the limits of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a schematic representation of a generic blending stationsuch as a gasoline blending station in a petroleum refinery, modifiedand operated in accordance with the process of the present invention.The drawing has been simplified by the deletion of a large number ofpieces of apparatus customarily employed on a process of this naturewhich are not specifically required to illustrate the performance of thesubject invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention is a process of controlling the value of at least onecharacteristic in a blended composition resulting from the blending ofvarious stock components. Although many types of components may beblended to form a wide variety of products, in the typical case, thecomponents are petroleum refinery streams which are blended to form apetroleum product. For example, the blended product may be, but is notlimited to, gasoline, jet fuel, diesel fuel, lubricating oils, andothers. The characteristics for which the blending is controlled may beone or more of a number of characteristics such as, but not limited to,octane number, cetane number, RVP, specific gravity, and viscosity, andpercentage content of benzene, aromatics, ethers, alcohols, and others.Furthermore, additional considerations or economic weightings other thanquality parameters, physical properties or compositional characteristicscould also be controlled. Material costs and blending componentavailability, for example, could be included. Which characteristics arecontrolled generally depends on the desired petroleum product. Forexample, if the product is gasoline, the characteristics controlled mayinclude octane number and RVP; if the product is diesel fuel, thecharacteristic controlled for may be cetane number; and, if the productis lubricating oil, the characteristics controlled may includeviscosity.

In general terms, the apparatus necessary to perform the presentinvention in a typical case includes feed lines, having flow sensors andflow controllers connected to a computer, which provide the componentsto a mixing chamber, a product line which conducts the blended productaway from the mixing chamber, and a means for analyzing the productwhich is also connected to the computer. Also in general terms, theinvention is performed by first setting the proportion of the componentsto previously selected values and then determining the initial values,V_(l), of one or more characteristics of the product. The proportions ofthe components are then temporarily varied, during each variation thevalues of the characteristics of the product are determined, and thechanges in those values from the initial values are calculated. Thevariations in the proportions of the components may then be related tothe resulting changes in the values of said characteristics by asuitable algorithm. The proportions of the components may then beadjusted according to a suitable algorithm and the values of thecharacteristics in the new composition, V_(N), may then be determined.The process is repeated, varying the proportions of the components,determining the variation in the values of the characteristics, andadjusting the proportion of the components, so that the values of thecharacteristics in each new composition become numerically closer to thetarget values, V_(T), of the characteristics. This progression can berepresented as |V_(T) -V_(N) |≦|V_(T) -V_(l) |. It is not necessary thatthe target values of the characteristics be met exactly, it issufficient that the values of the product composition be within ±δ ofthe target values. The value of δ depends on the characteristic beingcontrolled, and is the industry accepted variability for thatcharacteristic. For example, when the characteristic is octane number,the δ would be about 0.3 octane number and when the characteristic isRVP, the value of δ would be about 0.2 psi. The preceding steps would berepeated until |V_(T) -V_(N) |≦δ. Once this point is reached, theproceeding steps only need to be repeated periodically to verify that|V_(T) -V_(N) | has not become greater than δ, or when any processingchange is made. It is contemplated that, the variations and adjustmentswould be performed automatically by way of a feedback loop responding tothe results of the determinations of the values of the characteristics.

It is important to note that the amount by which the proportion of thecomponents is varied is preferably kept sufficiently small so that eachvariation alters the values of the characteristics in the final blendedproduct only slightly as compared to the previously measured blendedcomposition. Generally, the preferred embodiment is that where thevalues of the characteristics are altered by about the corresponding δor less. For example, in a preferred embodiment, the componentproportion variations are preferably sufficiently small so that thevalue of the octane number of the final blended product is altered byonly about 0.1 to about 0.3 octane numbers. Controlling the blendingthrough such small incremental changes in the values of thecharacteristics is possible since the noise level of the spectroscopicmeasurements is surprisingly low. This invention, through capitalizingon the low noise level of the measurements and using relatively smallincrements, adds an increased degree of precision to the overallcontrol. Furthermore, allowing only relatively small incremental changesin the values of the characteristics minimizes non-linear effects thatmay arise from the combination of the blending stock components. Whileit is preferred, the invention is not limited to such small variations,and larger variations which result in larger changes in the values ofthe characteristics, e.g., up to one octane number, are contemplated.

It is not important, however, in what order the proportions of thecomponents are varied. In fact, although it is an option, it is notnecessary that the proportion of each component be varied individually.It is within the scope of this invention to vary the proportions of thecomponents individually, in pairs, or in groups of three or more.

Determinations of the values of the characteristics pursuant to thisinvention are made by first obtaining the NIR absorbance, reflectance,or transmission spectrum of the blended composition and then calculatingthe values of said characteristics according to a predeterminedalgorithm relating said characteristics to the spectrum. The actualwavelength range is not important to specify here since it is possibleto use wavelengths which span the entire near infrared range of about700 to about 2,500 nm. However, the range of about 900 to about 2,000 nmis preferred due to the superior signal to noise ratio observed whenworking in this range, and the range of about 1,100 to about 1,600 ismost preferred. Such optical measurements are known in the art, as areseveral mathematical algorithms for analyzing the spectral data,including but not limited to, partial least squares with latentvariables, multivariant regression, principal component regression andGauss Jordan type row reduction. See generally, DiFoggio, R; Sadhukhan,M.; Ranc, M. L.; Off & Gas J. May 3, 1993, 87-90. It is furthercontemplated that, where appropriate, the exact numerical values of thecharacteristic need not be determined. The blending control, althoughless efficient, may be accomplished with only the determination ofwhether a variation in the proportion of the components causes anincrease or a decrease in the value of the characteristic.

Applying NIR spectroscopy contributes to the superior efficiency of theinvention since the technique requires no sample preparation, and isaccurate, rapid and non-destructive. Furthermore, NIR spectroscopy canbe performed on-line, where the sample is automatically routed to thespectrophotometer, or in-line, where a probe or waveguide is placeddirectly in the stream. One example of a suitable optical probe isfurther disclosed in U.S. Pat. No. 4,786,171, which is incorporatedherein by reference. Other such spectrophotometric equipment is wellknown in the art. The time necessary to obtain the spectrum andcalculate results is generally less than one minute, and the samespectrum may be used to calculate the values of various characteristics.These factors result in data being available in real-time, which whenused in the present invention translates into the ability to preciselyand efficiently control the value of a characteristic.

While NIR spectroscopy is preferred, other spectroscopic techniquescould be used in lieu of NIR spectroscopy. Mid-range infraredspectroscopy or Fourier-transform infrared spectroscopy may be usedwhere the characteristic may be measured in the range of about 2,500 toabout 25,000 nm. Once again, the actual wavelength range is not criticalto the success of the invention since it is possible to use wavelengthsthat span the entire mid-range infrared and Fourier-transform infraredregion. However, the most useful and therefore preferred wavelengthranges are about 2,500 to about 4,000 nm, and about 2,800 to about 3,200nm. Examples of measurements in the mid-range infrared region may befound in Fodor, G. E.; Kohl, K. B. Energy and Fuels, 1993, 7, 598-601.Where appropriate, one spectroscopic technique may be substituted foranother without affecting the other steps in the practice of thisinvention.

Without intending any limitation on the scope of the present invention,and as merely illustrative, this invention is explained below inspecific terms as applied to the preferred embodiment of controlling theoctane number of a blended gasoline to obtain a specific grade gasolinehaving a desired octane number. The necessary apparatus is firstdescribed, and then the process of the invention as applied to thepreferred embodiment is discussed. For ease of understanding, theprocess of the invention is described below as the sequential variationof individual components and as just mentioned, control of the value ofonly one characteristic.

Turning now to the apparatus as illustrated in the drawing, severalinput lines 12, 14, 16, 18, 20, and 22 supply the stock components tothe blending chamber 23 in which the stock components are mixed to formthe blended gasoline. It should be understood that a greater or lessernumber of input lines may be employed depending upon the blendingprocess involved, stock components available, and the preferences of theparticular refiner. The blended gasoline is conducted through an outputconduit 26 to some storage facility such as a holding tank (not shown)or transferred downstream to a pipeline (not shown). Each of the inputlines 12-22 is provided with an associated flow rate sensor and flowcontrol valve, respectively indicated as a unit at 28, 30, 32, 34, 36,and 38. The output conduit 26 is provided with an optical sampling cell40 that is coupled to a spectrophotometer 42 by a fiber optic cable orplaner waveguide 44.

The spectrophotometer 42 is coupled by a data bus 50 to a generalcontrol system computer 48. Each of the flow rate sensors and flowcontrol valves 28-38 are similarly respectively coupled to the computer48 via data buses 54-64. The control system computer 48 monitors boththe flow rates of the blending stock components through the input lines12-22 and the data provided by the spectrophotometer 42 in order to varythe flow rates in the input lines 12-22 by appropriate commands to theassociated flow control valve.

Using the described apparatus, the invention as applied to the preferredembodiment of controlling the octane number of a blended gasoline toobtain a specific grade gasoline having a desired octane number isperformed as follows. The flow rates of each of the feed lines 12-22,and therefore the proportion of each component, may be first set toselected values based on the refiner's experience, laboratory data, orblending equations. The value of the initial octane number may then bedetermined by obtaining the NIR spectral profile of the blended gasolineflowing through the output conduit 26 over the range of 900 to 2,000 nmand analyzing the spectral profile according to, e.g., a partial leastsquares with latent variables type mathematical technique. The flow ratethrough feed line 12 might then be changed and the value of the octanenumber of the now altered gasoline flowing out of the mixing chamber 23and through the output conduit 26 may be again determined using thespectrophotometer 42 to obtain and analyze a new NIR spectral profile.The flow rate through feed line 12 may then be returned to its initialsetting, and the flow rate through another feed line, such as feed line14, might be varied. The value of the octane number of the again alteredblended gasoline may be again determined by obtaining and analyzinganother spectral profile with the spectrophotometer 42, after which theflow rate through 14 may also be returned to its initial setting. Thisprocess may be repeated for each of the remaining feed lines 16-22 withthe value of the octane number of the blended gasoline being determinedafter the flow rate through each feed line had been altered, and beforethe flow rate had been returned to its initial setting. Once each feedline has been individually and sequentially altered and the resultingeffect on the value of the octane number of the blended gasolinerecorded, the flow rate of one or more of the feed lines may be resetaccording to an algorithm to afford a product whose octane number iscloser to the target value than was the octane number of the initialproduct. The new value of the octane number of the gasoline formed bythis altered blending of the components might then be determined and theforegoing procedure repeated until the value of the octane number of theproduct composition is within ±0.3 octane numbers of the desired ortarget octane number.

It must be emphasized that the above description is merely illustrativeof a preferred embodiment, and is not intended as an undue limitation onthe generally broad scope of the invention. Moreover, while thedescription is narrow in scope, one skilled in the art will understandhow to extrapolate to the broader scope of the invention. For example,the procedure for the simultaneous variation of groups of feed lines orfor the simultaneous control of more than one characteristic can bereadily extrapolated from the foregoing description.

In an alternative embodiment of the present invention, blending octanenumbers can be directly determined and used in existing blendingequations thereby improving the accuracy and usefulness of the blendingequations. As previously mentioned, the blending octane number of astock component which is applied in the blending equation, may differ inimpact on the octane number of the finished blend depending on thepresence or absence of other blending components. Therefore, being ableto accurately determine blending octane numbers that apply specificallyto the matrix of components being used allows for more accurate resultsfrom blending equations. The blending octane number of a blending stockcomponent can be derived from:

    [O.sub.x ][ΔL.sub.x ]+[O.sub.k ][L.sub.T ]=[O.sub.T ][L.sub.T +ΔL.sub.X ]                                         [1]

or

    O.sub.x =O.sub.T +ΔO.sub.x [L.sub.T /ΔL.sub.x ][2]

where:

O_(x) =the blending octane number of feed line x

O_(k) =the octane number of the blended gasoline before any incrementalchange in the flow rate of feed line x

O_(T) =the octane number of the blended gasoline after an incrementalchange in the flow rate of feed line x

L_(T) =the total volume of blended gasoline

ΔL_(x) =the incremental volume change of feed line x

ΔO_(x) =the incremental change in the octane number of the blendedgasoline

Thus, in this embodiment of the present invention, preexisting blendingequations may be more effectively applied by using octane numbers forthe blending stock components that are obtained through the applicationof equations [1] or [2], above. To perform this embodiment, first theflow rates for each of the feed lines x would be set to selected values,then the values of O_(k) and L_(T) would be measured, and finally, theflow rates for each of the feed lines would be sequentially varied withmeasurements of ΔL_(x) and O_(T) taken and ΔO_(x) calculated after eachchange in a feed line flow rate. The blending octane numbers O_(x) ofeach blending stock component could then be derived from equations [1]or [2], above. These derived blending octane numbers are specific to thematrix at hand, and using these derived blending octane numbers inexisting blending equations provides more accurate results than thecurrent practice of using blending octane numbers based on the refiner'sgeneral experience.

What is claimed is:
 1. A process for continuously controlling the valueof at least one characteristic of a petroleum product compositionresulting from the blending of N components, where the initial value ofthe characteristic in the product composition is V_(l), where the finalvalue of the characteristic in the product composition is to be within±δ of a target value V_(T) and where the value of said characteristic isdetermined by obtaining the near infrared spectrum of the productcomposition over the range of about 700 to about 2,500 nm andcalculating the value of said characteristic in the product compositionaccording to a predetermined first algorithm relating saidcharacteristic to the spectrum, comprising:a. varying the proportions ofthe components to afford a series of intermediate product compositions;b. determining the value of said characteristic in each of saidintermediate product compositions and calculating therefrom the changein said value associated with the variation in each componentproportion; c. adjusting the proportions of the components according toa second algorithm, said algorithm relating the variation of eachcomponent proportion to the resulting change in the value of saidcharacteristic in said intermediate product composition, to afford a newproduct composition whose new value of said characteristic is V_(N) andwhere |V_(T) -V_(N) |≦|V_(T) -V_(l) |; and d. repeating steps a)-c)until |V_(T) -V_(N) |≦δ.
 2. The process of claim 1 where the proportionsof the components are varied by amounts affording changes in the valueof said characteristic of δ or less.
 3. The process of claim 1 where thecharacteristic is selected from the group consisting of octane number,cetane number, Reid vapor pressure, specific gravity, viscosity,aromatic content, benzene content, ether content, and alcohol content.4. The process of claim 1 where the near infrared spectrum is obtainedover the range of about 900 to about 2,000 nm.
 5. The process of claim 1where the near infrared spectrum is obtained over the range of about1,100 to about 1,600 nm.
 6. The process of claim 1 where the proportionof each component is varied singularly.
 7. The process of claim 1 wherethe proportions of the components are varied in groups of two or more.8. The process of claim 1 where two or more characteristics arecontrolled simultaneously.
 9. The process of claim 1 where the nearinfrared spectrum is obtained on-line.
 10. The process of claim 1 wherethe near infrared spectrum is obtained in-line.
 11. The process of claim1 where the product composition is gasoline, and where thecharacteristic is selected from the group consisting of octane number,Reid vapor pressure, specific gravity, viscosity, aromatic content,benzene content, ether content, and alcohol content.
 12. A process forcontinuously controlling the value of at least one characteristic of aproduct composition resulting from the blending of N components, wherethe initial value of the characteristic in the product composition isV_(l), where the final value of the characteristic in the productcomposition is to be within ±δ of a target value V_(T) and where thevalue of said characteristic is determined by obtaining a spectrum ofthe product composition where said spectrum is generated by aspectroscopic technique selected from the group consisting of nearinfrared spectroscopy over the range of about 700 to about 2,500 nm,mid-range infrared spectroscopy over the range of about 2,500 to about25,000 nm, and Fourier-transform infrared spectroscopy over the range ofabout 2,500 to about 25,000 nm, and calculating the value of saidcharacteristic in the product composition according to a predeterminedfirst algorithm relating said characteristic to the spectrum,comprising:a. varying the proportions of the components to afford aseries of intermediate product compositions; b. determining the value ofsaid characteristic in each of said intermediate product compositionsand calculating therefrom the change in said value associated with thevariation in each component proportion; c. adjusting the proportions ofthe components according to a second algorithm, said algorithm relatingthe variation of each component proportion to the resulting change inthe value of said characteristic in said intermediate productcomposition, to afford a new product composition whose new value of saidcharacteristic is V_(N) and where |V_(T) -V_(N) |≦|V_(T) -V_(l) |; andd. repeating steps a)-c) until |V_(T) -V_(N) |≦δ.
 13. The process ofclaim 12 where the proportions of the components are varied by amountsaffording changes in the value of said characteristic of δ or less. 14.The process of claim 12 where the characteristic is selected from thegroup consisting of octane number, cetane number, Reid vapor pressure,specific gravity, viscosity, aromatic content, benzene content, ethercontent, and alcohol content.
 15. The process of claim 12 where saidnear infrared spectroscopy range is about 900 to about 2,000 nm, saidmid-range infrared spectroscopy range is about 2,500 to about 4,000 nm,and said Fourier-transform infrared spectroscopy range is about 2,500 toabout 4,000 nm.
 16. The process of claim 12 where said near infraredspectroscopy range is about 1,100 to about 1,600 nm, said mid-rangeinfrared spectroscopy range is about 2,800 to about 3,200 nm, and saidFourier-transform infrared spectroscopy range is about 2,800 to about3,200 nm.
 17. The process of claim 12 where the proportion of eachcomponent is varied singularly.
 18. The process of claim 12 where theproportions of the components are varied in groups of two or more. 19.The process of claim 12 where two or more characteristics are controlledsimultaneously.
 20. The process of claim 12 where said spectrum isobtained on-line.
 21. The process of claim 12 where said spectrum isobtained in-line.
 22. The process of claim 12 where the productcomposition is gasoline, and where the characteristic is selected fromthe group consisting of octane number, Reid vapor pressure, specificgravity, viscosity, aromatic content, benzene content, ether content,and alcohol content.
 23. The process of determining the blending octanenumbers of N components which are blended to form a blended gasoline ofvolume L_(T), where the initial value of the octane number of theblended gasoline, O_(k), is determined by obtaining the near infraredspectrum of the blended gasoline over the range of about 700 to about2,500 nm and calculating the value of the octane number in the blendedgasoline according to a predetermined algorithm relating said octanenumber to the spectrum, comprising:a. varying the proportion of saidcomponents by an amount, ΔL_(x), to afford a series of new blendedgasolines; b. determining the value of the octane number in each of saidnew blended gasolines, O_(T), and calculating therefrom the change,ΔO_(x), in said octane number associated with the variation inproportion of each component by the equation ΔO_(x) =O_(k) -O_(T) ; andc. determining the blending octane number, O_(x), of each componentaccording to the formula: O_(x) =O_(T) +ΔO_(x) [L_(T) /ΔL_(x) ].
 24. Theprocess of claim 23 where the proportion of a component is varied by anamount such that ΔO_(x) ≦0.3.
 25. The process of claim 23 where the nearinfrared spectrum is obtained over the range of about 900 to about 2,000nm.
 26. The process of claim 23 where the near infrared spectrum isobtained over the range of about 1,100 to about 1,600 nm.
 27. Theprocess of claim 23 where the near infrared spectrum is obtainedon-line.
 28. The process of claim 23 where the near infrared spectrum isobtained in-line.
 29. The process of determining the blending octanenumbers of N components which are blended to form a blended gasoline ofvolume L_(T), where the initial value of the octane number of theblended gasoline, O_(k), is determined from a spectrum of the blendedgasoline generated by a spectroscopic technique selected from the groupconsisting of near infrared spectroscopy over the range of about 700 toabout 2,500 nm, mid-range infrared spectroscopy over the range of about2,500 to about 25,000 nm, and Fourier-transform infrared spectroscopyover the range of about 2,500 to about 25,000 nm, and calculating thevalue of the octane number of the blended gasoline according to apredetermined algorithm relating said octane number to the spectrum,comprising:a. varying the proportion of said components by an amount,ΔL_(x), to afford a series of new blended gasolines; b. determining thevalue of the octane number in each of said new blended gasolines, O_(T),and calculating therefrom the change, ΔO_(x), in said octane numberassociated with the variation in proportion of each component by theequation ΔO_(x) =O_(k) -O_(T) ; and c. determining the blending octanenumber, O_(x), of each component according to the formula O_(x) =O_(T)+ΔO_(x) [L_(T) /ΔL_(x) ].
 30. The process of claim 29 where theproportion of a component is varied by an amount such that ΔO_(x) ≦0.331. The process of claim 29 where said near infrared spectroscopy rangeis about 900 to about 2,000 nm, said mid-range infrared spectroscopyrange is about 2,500 to about 4,000 nm, and said Fourier-transforminfrared spectroscopy range is about 2,500 to about 4,000 nm.
 32. Theprocess of claim 29 where said near infrared spectroscopy range is about1,100 to about 1,600 nm, said mid-range infrared spectroscopy range isabout 2,800 to about 3,200 nm, and said Fourier-transform infraredspectroscopy range is about 2,800 to about 3,200 nm.
 33. The process ofclaim 29 where the spectrum is obtained on-line.
 34. The process ofclaim 29 where the spectrum is obtained in-line.